| AVS 60th International Symposium and Exhibition | |
| Advanced Surface Engineering | Thursday Sessions |
| Session SE+PS-ThM |
| Session: | Pulsed Plasmas in Surface Engineering (8:00-10:00 am)/Atmospheric Pressure Plasmas (10:40 am-12:00 pm) |
| Presenter: | A.A. Voevodin, Air Force Research Laboratory, Wright Patterson Air Force Base |
| Authors: | A.N. Reed, Air Force Research Laboratory, Wright Patterson Air Force Base P.J. Shamberger, Air Force Research Laboratory, Wright Patterson Air Force Base C. Muratore, University of Dayton J.E. Bultman, University of Dayton Research Institute A.A. Voevodin, Air Force Research Laboratory, Wright Patterson Air Force Base |
| Correspondent: | Click to Email |
High power impulse magnetron sputtering (HiPIMS) was demonstrated for the first time on semiconducting zinc oxide thin films for use as a transistor channel material. Nanocrystalline ZnO thin film transistors are of interest for integrated RF devices due to their high mobilities (110 cm2V-1s-1) and high on-off ratios (up to 1012) [1]. These electrical transport properties are critically dependent on film microstructure, defect densities, crystal orientation, surface roughness and grain size. Due to a highly ionized flux, HiPIMS allows for control of thin film microstructure, while simultaneously producing high quality crystalline films on unheated substrates. However the use of HiPIMS for the growth of oxide semiconductors and their resulting electrical transport properties remain largely unexplored.
In this study, we investigate the interrelationship between the plasma characteristics, resulting film microstructure, and the electrical transport properties of nanocrystalline ZnO thin films. HiPIMS was used to deposit thin (~100 nm) ZnO films from ceramic ZnO and metallic Zn targets onto substrates heated to 150 oC. In both non-reactive and reactive cases, the resulting films had stronger crystallinity, more highly aligned (002) texture and lower surface roughness than films grown with pulsed DC sputtering, as determined by XRD, SEM and AFM measurements. The degree of alignment in the films was strongly dependent on the target potential, gas pressure and pulsing parameters. Film I-V characteristics were compared alongside microstructures to correlate electrical transport properties with specific aspects of microstructure (grain size, crystallinity, texture). Similarly, time-resolved current measurements of the target and ion energy distributions, determined using energy resolved mass spectrometry, were correlated to film microstructure in order to investigate the effect of plasma conditions on film nucleation and growth. Finally, we will compare ZnO films grown by HiPIMS against those grown by other techniques (pulsed DC sputtering, pulsed laser deposition) and will critically evaluate the capability of HiPIMS for the deposition of electronic oxide films.
[1] B. Bayraktaroglu, K. Leedy, R. Neidhard. Microwave ZnO Thin Film Transistors. IEEE Electronic Device Letters V 29 Iss. 9, 1024-1026 2008